KR101366923B1 - Method for preparing spherical ceramic foam and spherical ceramic foam prepared by the same - Google Patents

Abstract

There is provided a spherical ceramic foam manufacturing method and a spherical ceramic foam produced thereby.
Spherical ceramic foam manufacturing method according to the present invention comprises the steps of adding agar solution to the aerated ceramic slurry; Adding a ceramic slurry to which the agar solution is added to oil; Separating the slurry from oil and then drying; And sintering the dried slurry. According to the present invention, a spherical ceramic foam is manufactured by simultaneously using a method of gelling agar in a drop-in-oil method of forming drops in oil. do. According to the present invention, it is possible to manufacture a spherical ceramic foam with improved pore properties, size and size uniformity, there is an advantage that the physical parameters of the spherical ceramic foam can be controlled.

Description

Method for preparing spherical ceramic foam and spherical ceramic foam prepared thereby {Method for preparing spherical ceramic foam and spherical ceramic foam prepared by the same}

The present invention relates to a method for manufacturing a spherical ceramic foam and a spherical ceramic foam produced thereby, more specifically, it is possible to manufacture a spherical ceramic foam with improved pore characteristics, size and uniformity of the size, the control of physical parameters of the spherical ceramic foam It relates to a spherical ceramic foam manufacturing method and the spherical ceramic foam produced thereby has the advantage that it is possible.

Ceramic foams exhibit unusual physical properties such as low bulk density, high specific surface area, and good permeability. Due to these properties, ceramic foams can be used as biocatalyst supports and biomaterials. Although ceramic foams can be prepared by different synthetic methods, ceramic foams with various pore structures (e.g. porosity, pore size and pore morphology) have yet to be studied for producing spherical ceramic foam materials. There is no bar. Spherical ceramic foams (SCF) can be used in materials such as catalyst support media in fluid support systems, for example, which provide superior packing uniformity in spherical ceramic foams compared to bulk form materials. This is because it has a strong resistance to thermal shocks from the outside, and less damage loss due to a collision than other forms.

Colloidal template methods, emulsion methods and granulation of ceramic slurries by vibration, pressing or spray drying have been reported as methods for producing spherical ceramic materials (including foams), but these methods have low porosity and / or millimeter or less. There is a limitation limited to the production of spherical ceramic materials having levels of magnitude. Lee and Park et al. Disclose an example of developing a pseudo-double-emulsion (PDE) method to produce spherical ceramic foams. The above method enables the production of high porosity ceramic particles, but has a limitation in that the size distribution of the ceramic foam is very wide and it is difficult to control the diameter of the particles. Size uniformity can be improved by sieving after processing, but this leads to an increase in process costs and damage to the final product. Recently, oil-drop methods based on sol-gel reactions have been reported as alternatives to the production of large spherical materials. Although the size uniformity of the pellets can be improved by this method, it is difficult to obtain pellets of macropores having a size of 2 mm or more. This represents a limitation of the size control that the scheme has. Various other methods have been proposed, but there is still a problem that the size reproducibility of the sphere is not good or the size control is difficult.

Therefore, the problem to be solved by the present invention is to provide a method for producing a spherical ceramic foam having a uniform size, excellent porosity characteristics.

Spherical slurry foam manufacturing method according to an embodiment of the present invention for achieving the above object comprises the steps of adding an agar solution to the aerated ceramic slurry; Adding a ceramic slurry to which the agar solution is added to oil; Separating the slurry from oil and then drying; And sintering the dried slurry.

In one embodiment of the invention the oil is paraffin oil.

In one embodiment of the present invention, the aeration of the ceramic slurry and the addition of the agar solution proceeds below 60 degrees Celsius.

In one embodiment of the present invention, the ceramic is any one selected from the group consisting of alumina, magnesia, zirconia, carsia, silica and yttria.

In one embodiment of the present invention, as the agar concentration of the agar solution increases, the porosity and specific surface area of the prepared spherical ceramic foam increase.

In one embodiment of the present invention, the slurry includes poly (acrylic acid) as a dispersant.

In one embodiment of the present invention, the bubbled slurry is prepared by adding sodium lauryl sulfate as a foaming agent to the slurry solution.

In one embodiment of the invention the sintering proceeds at a temperature of 1500 degrees Celsius or more.

In one embodiment of the invention the slurry is injected into the oil in the form of drops.

In one embodiment of the invention said injecting injects said slurry into oil via a syringe.

In one embodiment of the present invention, the size of the spherical ceramic foam increases as the concentration of the agar solution increases.

In one embodiment of the present invention, the size distribution of the spherical ceramic foam is the narrowest when the concentration of the agar solution is 1.00% by weight.

The present invention provides a spherical ceramic foam produced by the above-described method, in order to solve the another problem.

In one embodiment of the present invention, the ceramic is any one selected from the group consisting of alumina, magnesia, zirconia, carsia, silica and yttria.

According to the present invention, spherical ceramic foams are prepared by simultaneously using a drop-in-oil method of forming a drop in oil and a method of gelling agar. According to the present invention, it is possible to manufacture a spherical ceramic foam with improved pore properties, size and size uniformity, there is an advantage that the physical parameters of the spherical ceramic foam can be controlled.

1 is a step diagram of a spherical ceramic foam manufacturing method according to an embodiment of the present invention.
2A and 2B are SEM images showing the surface and cross section of a spherical ceramic foam made in accordance with the present invention.
3 is a table summarizing pore characteristics and specific surface area of spherical ceramic foams prepared at various agar concentrations.
4A-4D are photographs of spherical ceramic foams produced at various agar concentrations.
5 is a graph of the size distribution of spherical ceramic foams prepared at various agar concentrations.

The following embodiments are detailed description to help understand the present invention, and it should be understood that the present invention is not intended to limit the scope of the present invention. Accordingly, equivalent inventions performing the same functions as the present invention are also within the scope of the present invention.

In addition, in adding reference numerals to the constituent elements of the drawings, it is to be noted that the same constituent elements are denoted by the same reference numerals even though they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

The present invention provides a method for producing a spherical ceramic structure (foam) having a uniform size and excellent pore properties in order to overcome the above-mentioned limitations of the prior art. The drop-in-oil method and the gelation method of agar (agar) in a gel form were combined. Furthermore, the size distribution, uniformity and pore characteristics of spherical ceramic foams were synthesized for various amounts of gelling agent (ie, agar).

1 is a step diagram of a spherical ceramic foam manufacturing method according to an embodiment of the present invention.

Referring to Figure 1, first, agar solution is added to the bubbled ceramic slurry.

Thereafter, the ceramic slurry to which the agar solution is added is added to the oil to form a particulate form in a drop-in-oil manner. Again, the agar-added-slurry droplets in the form of granules are separated from the oil and then dried, and the dried slurry is then sintered at high temperature. Hereinafter, a spherical silicone foam manufacturing method according to the present invention will be described in more detail as an experimental example.

Example

synthesis

Alumina having a specific surface area of 6.0 m ² / g (A34; NLM Co., Tokyo, Japan) was used as a starting material. Poly (acrylic acid) (PAA, Aldrich Co., St. Louis, MO) and sodium lauryl sulfate ((SLS) (Samchun Pure Chemical Co., Seoul, Korea)) were used as dispersants and foaming agents for foam formation, respectively. Agar (MSA Co., Seoul, Korea), which can be purchased as a gelling reagent, was used as a gelling reagent, and the agar solution was induced to rapid gelation at low temperature, and the obtained gelling product showed high gel strength even at low solid concentration.

The alumina slurry concentrations were 50% by weight and 0.08% by weight. PAA was added to the slurry to improve particle stability. Homogenization of the aluminum slurry was carried out by mechanical mixing, followed by milling and abrasion in a jar with alumina balls at 500 rpm for 1 hour.

Aqueous agar solution added to the alumina slurry was prepared at four different concentrations, which were 0.50, 0.75, 1.00 and 1.50% by weight relative to the dried alumina. The water-soluble agar solutions of various concentrations were prepared by adding 2, 3, 4 and 6 g of agar powder to 100 mL of distilled water and heating the mixture at 90 degrees Celsius for 1 minute.

Foaming of the alumina slurry proceeded below 60 degrees Celsius, thereby avoiding sudden solidification of the agar solution. Four sodium lauryl sulfate were added to the slurry, and the slurry was bubbled at an extension ratio of 1.5, which is the ratio of the bubbled slurry volume to the original slurry volume.

After cooling the prepared agar solution below 60 degrees Celsius, the cooled agar solution was added to the bubbled slurry solution. The weight ratio between the initial alumina slurry and the agar solution is 2: 1. The mixture was then mixed at 60 degrees Celsius for 1 minute.

After addition of the agar solution, the final concentration of the alumina slurry was 34% by volume. The slurry to which the agar solution was added was dropped on a liquid paraffin column (height: 50 cm, temperature: 5 degrees Celsius) using a syringe. At this time, the inner diameter of the syringe was 2.4 mm, and the bubbled slurry in which the agar solution was added was injected into paraffin oil at a flow rate of 640 mL / h. Thereafter, the bubbled spherical droplets were separated from the liquid paraffin oil and dried at room temperature for 24 hours. The dried spherical droplets were sintered at 1550 degrees Celsius for more than 1,500 degrees Celsius for 2 hours, with a temperature rise rate of 3 degrees Celsius per minute.

Experimental Example

Measurement method

The overall porosity of the spherical ceramic foams produced at different agar amounts was determined in the following manner. First, the bulk density was determined by measuring the volume and weight of the spherical ceramic foam. The absolute density of alumina (3.98 g / cm3) and the apparent density of the spherical ceramic foam were obtained using a helium pycnometer, and again the open porosity and the closed porosity were calculated from experimentally measured values (bulk, absolute and apparent density). It was. The microstructure and surface morphology of the spherical ceramic foams prepared according to the invention were analyzed using a scanning electron microscope, and the specific surface area of the spherical ceramic foams was measured using BET. The size distribution of spherical ceramic foams prepared in various agar quantities was determined using an optical microscope equipped with an image analyzer. In order to compare the size uniformity of spherical ceramic foams prepared at various agar concentrations, the coefficient of variation value was calculated according to the following equation.

[Mathematical Expression]

는 수 평균 직경, 그리고 N는 구형 세라믹 폼의 전체 수이다.
Where d _i is the i th diameter,

Is the number average diameter, and N is the total number of spherical ceramic foams.

Analysis

2A and 2B are SEM images showing the surface and cross section of a spherical ceramic foam made in accordance with the present invention.

2A and 2B, it can be seen that a large number of pores are formed on the inner and outer surfaces of the spherical ceramic foam, and these pores are interconnected to a considerable level, indicating that they are open. However, different pore characteristics appeared depending on the agar concentration, which is shown in the table of FIG. 3. In particular, the total and open porosity and specific surface area of the spherical ceramic foam according to the invention increased with the amount of agar. This result is believed that an increase in the amount of agar leads to the formation of a pore window defined as a new pore formed by two adjacent pore contacts, which means that the space occupied by the agar is replaced by voids during the sintering process. Because it becomes.

4A-4D are photographs of spherical ceramic foams produced at various agar concentrations.

4A to 4D, it can be seen that the size of the spherical ceramic foam increases with increasing agar concentration. In particular, the average size of the spherical ceramic foams was measured at 1.4, 1.6, 2.6 and 3.0 mm, respectively, for agar concentrations of 0.5, 0.75, 1.00 and 1.5% by weight (see FIG. 5).

Furthermore, high proportions of spherical ceramic foams with sizes of less than 2 mm were observed when the agar concentration was less than 1.00% by weight. However, at agar concentrations above 1.00% by weight, a small proportion of spherical ceramic foams of this size was observed.

The slurry bubbled with agar was dropped into paraffin using a syringe, and the size of the droplet formed near the drop was increased in proportion to the amount of agar. It is well known that the formation of spherical droplets is closely related to liquid surface tension, and increasing liquid density leads to stronger attraction between molecules, resulting in higher surface tension. Therefore, the tendency between increasing the size of the spherical ceramic foam and increasing the agar concentration can be explained by the increase in surface tension with the addition of agar.

Looking at the relationship between the size distribution of the spherical ceramic foam and the agar concentration, the spherical ceramic foam formed at agar concentration of 1.00% by weight showed the narrowest size distribution. That is, the size distributions were 0.7-2.4, 0.8-2.6, 2.0-2.9, and 2.2-4.0 mm at concentrations of 0.50, 0.75, 1.00, and 1.50% by weight, respectively.

To analyze this result more quantitatively, the C.V. The figures were calculated and compared.

Calculated C.V. Values were 24.6%, 18.2%, 7.2%, and 15.6% for agar concentrations of 0.50, 0.75, 1.00, and 1.50% by weight, respectively. This means that the size uniformity of the spherical ceramic foam is highest when the agar concentration is 1.0% by weight. The result means that the size of the spherical ceramic foam can be effectively controlled by adjusting the agar pad. In order to demonstrate the effect of the spherical ceramic foam manufacturing method according to the present invention in terms of size uniformity, the C.V. The values were compared. The C.V value of the spherical ceramic foam produced by the PDE method was 31%, which means that the drop-in-oil method according to the agar addition method according to the present invention was improved over the prior art.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

Claims (14)

Spherical ceramic foam manufacturing method, the method
Adding an agar solution to the bubbled ceramic slurry;
Adding a ceramic slurry to which the agar solution is added to oil;
Separating the slurry from oil and then drying; And
Sintering the dried slurry,
Bubble of the ceramic slurry and the addition of the agar solution proceeds to 60 degrees Celsius or less,
The slurry is a spherical ceramic foam manufacturing method comprising a poly (acrylic acid) as a dispersant. The method of claim 1,
Spherical ceramic foam manufacturing method characterized in that the porosity (porosity) and specific surface area of the prepared spherical ceramic foam increases as the agar concentration of the agar solution increases. The method of claim 1,
The slurry is spherical ceramic foam manufacturing method characterized in that the oil is injected in the form of drops. The method of claim 3, wherein
Wherein said injecting injects said slurry into oil through a syringe. The method of claim 1,
Spherical ceramic foam manufacturing method characterized in that the size of the spherical ceramic foam increases as the concentration of the agar solution increases. The method of claim 1,
The size distribution of the spherical ceramic foam is the sphere ceramic foam manufacturing method characterized in that the narrowest when the concentration of the agar solution is 1.00% by weight. delete delete delete delete delete delete delete delete

Images